Removable liner for gear pump

ABSTRACT

A hydraulic pump of the intermeshing spur gear type has a onepiece liner for the gear cavity in the body. The liner is a Cshaped piece of resilient metal coated with bearing material and in its free state, is larger than the cavity and requires elastic compression to be inserted therein. The inlet passage is formed with three branches for improved filling at high speeds.

United States Patent Pettibone et a1.

[ 51 Aug. 1, 1972 REMOVABLE LINER FOR GEAR PUMP Inventors: Raymond B.Pettibone, Troy; Albin J. Niemiec, Sterling Heights, both of Mich.

Sperry Rand Corporation, Troy, Mich.

Filed: April 30, 1971 Appl. No.: 139,124

Assignee:

US. Cl. ..418/178, 418/179, 418/206 Int. Cl ..F04c l/08, F040 15/00Field of Search ..418/178, 179, 206

[56] References Cited UNITED STATES PATENTS 1,339,565 5/1920 Lambert..418/179X 1,686,867 10/1928 Kuhn ..418/206 X 1,927,395 9/1933 Edward..418/206 X 1,982,027 11/1934 Sieper ..418/206 X 2,697,987 12/1954Barclay ..418/206 X 2,966,860 1/1961 Maynard ..418/179 X PrimaryExaminer-Allan D. Herrmann Attorney-Theodore Van Meter 5 7 1 ABSTRACT 6Claims, 7 Drawing Figures PATENTEDAus 1 I972 3.680.990

' sumzorz INVENTORS ???W I11 I 177166 5 19 7 fliwv ATTORNEY usuallyeconomically unfeasible either to salvage the body or to replace it witha new one. v

It has been proposed to provide a removable liner for the gear pump bodywhich can be replaced when worn. However, previous attempts to do thishave failed because of the difficulty of holding the liner in place 7against the fluid pressure forces acting upon it. These tend to getbehind the liner, that is between the liner and the body, and causepremature wear, as well as allowing leakage from outlet to inlet behindthe liner.

Another difficulty with previous gear pumps lies in their limited speedpotential due to cavitation occurring at the inlet. A proposal toalleviate this problem is disclosed and claimed in the application ofPettibone et al., Ser. 63,192, filed Aug. 12, 1970 for PowerTransmission. The branched inlet passage there disclosed is satisfactoryfor pumps up to certain limits of tooth depth to width ratios, butbeyond this, the filling efficiency tends to fall off.

The foregoing difficulties are overcome by the present invention whichcomprises a hydraulic pump with a body having an ovoid cavity, a pair ofintermeshing gears mounted to rotate in the cavity, inlet and outletpassages in the body, the inlet passage being branched to enter thecavity at the end faces of the gears, and a liner for the ovoid surfaceof the cavity comprising a single piece of resilient sheet materialextending in contact with the tooth peripheries of both gears and acrossthe area adjacent the inlet, but having free ends providing an openingadjacent the outlet, the linear having a preformed free shape largerthan the cavity and being elastically compressed at its free ends to fitthe cavity.

The invention further comprises such a pump wherein the inlet passageincludes a third branch extending perpendicular to the plane containingthe gear axes and entering the cavity midway between the end faces ofthe gears.

IN THE DRAWINGS FIG. 1 is a transverse cross section of a gear pumpembodying a preferred form of the present invention.

FIG. 2 is a fragmentary cross section on line 2-2 of FIG. 1.

FIG. 3 is a side view of a liner incorporated in the pump of FIG. 1.

FIG. 4 is a view of the liner as seen from the plane 4-4 of FIG. 3.

FIG. 5 is a cross section on line 5-5 of FIG. 3.

FIG. 6 is a cross section on line 6-6 of FIG. 3.

FIG. 7 is a perspective view of a portion of the pump body and lineradjacent the inlet.

Referring to FIG. 1, the pump comprises a body 10 having an ovoid cavity12 within which the usual pair of meshing gears 14 is mounted forrotation. An inlet passage 16 and an outlet passage 20 are provided inthe body. As seen in FIG. 2, the inlet passage 16 has a pair of lateralbranches 18 which feed fluid to the end faces of the gear teeth and,more importantly, to the interdental spaces. A third branch 22 extendsstraight inwardly to the cavity 12 to carry a small portion of the totalinlet stream inwardly to a point midway between the end faces of thegears.

The cavity 12 is provided with a liner 24 which is of generally C-shapedconfiguration. It is illustrated in detail as a separate piece in FIGS.3 through 6 inclusive. The liner is preferably formed from sheet steelof a resilient or springy nature and is provided with a coating 26 ofaluminum or other bearing material suitable for low friction contactwith the tooth tips of the gears 14, and capable of wearing in to aclose fit with them. As illustrated in FIG. 3, the liner, in its freestate, is formed to be somewhat larger than the cavity 14. Thus, inorder to insert the liner into the cavity, the liner has to becompressed to the shape illustrated in dot-dash lines and then pushedinto the cavity. This results in a tight contact between liner andcavity with the highest pressure of contact existing at the two opentips of the liner where it is exposed to the highest fluid pressure.

Adjacent the third inlet branch 22 where it passes through the liner,the latter is provided with a pair of shallow depressions 28 forassisting in the induction of fluid from the branches l8 and 22 to theinterdental spaces. These depressions become progressively more shallowtoward their ends more distant from the inlet 22. By this configuration,it has been found that filling I efficiency is increased apparently dueeither to an effect similar to that of an impeller pump or to aninjector effect somewhatanalogous to a venturi, or to both.

The pump will include the usual additional elements of construction suchas bearings, drive shafts, seals, cheek plates, covers, and mountingflanges, all of which may be of known construction and are notillustrated in the present drawings.

We claim:

1. A hydraulic pump comprising a body having an ovoid cavity, a pair ofintermeshing gears mounted to rotate in the cavity, inlet and outletpassages in the body, the inlet passage being branched to enter thecavity at the end faces of the gears, and a liner for the ovoid surfaceof the cavity comprising a single piece of resilient sheet materialextending in contact with the tooth peripheries of both gears and acrossthe area adjacent the inlet, but having free ends providing an openingadjacent the outlet, the liner having a preformed free shape larger thanthe cavity and being elastically compressed at its free ends to fit thecavity.

2. A pump as defined in claim 1 wherein the liner is formed of sheetsteel having an adherent layer of bearing material on its inner surface.

3. A pump as defined in claim 2 wherein the layer is an aluminum alloy.

4. A pump as defined in claim 1 wherein the inlet p" sage includes athird branch extending perpendicular to the plane containing the gearaxes and entering the cavity midway between the end faces of the gears.

5. A pump as defined in claim 4 wherein the liner contains shallowdepressions extending from the end of the third inlet branch in thedirection of gear rotation.

6. A pump as defined in claim 5 wherein the depressions areprogressively shallower toward their distant ends.

1. A hydraulic pump comprising a body having an ovoid cavity, a pair ofintermeshing gears mounted to rotate in the cavity, inlet and outletpassages in the body, the inlet passage being branched to enter thecavity at the end faces of the gears, and a liner for the ovoid surfaceof the cavity comprising a single piece of resilient sheet materialextending in contact with the tooth peripheries of both gears and acrossthe area adjacent the inlet, but having free ends providing an openingadjacent the outlet, the liner having a preformed free shape larger thanthe cavity and being elastically compressed at its free ends to fit thecavity.
 2. A pump as defined in claim 1 wherein the liner is formed ofsheet steel having an adherent layer of bearing material on its innersurface.
 3. A pump as defined in claim 2 wherein the layer is analuminum alloy.
 4. A pump as defined in claim 1 wherein the inletpassage includes a third branch extending perpendicular to the planecontaining the gear axes and entering the cavity midway between the endfaces of the gears.
 5. A pump as defined in claim 4 wherein the linercontains shallow depressions extending from the end of the third inletbranch in the direction of gear rotation.
 6. A pump as defined in claim5 wherein the depressions are progressively shallower toward theirdistant ends.